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Moderate Variability Does Not Rule Out Metabolic Acidemia: A Finding Which May Change How We Conceptualize Fetal Heart Rate Monitoring

Published:December 21, 2017DOI:https://doi.org/10.1016/j.jogc.2017.10.007
      The 2008 National Institute of Child Health and Human Development (NICHD) Workshop Report on Fetal Heart Rate (FHR) Monitoring
      • Macones G.A.
      • Hankins G.D.
      • Spong C.Y.
      • et al.
      The 2008 National Institute of Child Health and Human Development workshop report on electronic fetal monitoring: update on definitions, interpretation, and research guidelines.
      states that, “moderate FHR variability reliably predicts the absence of fetal metabolic acidemia at the time it is observed.”
      • Macones G.A.
      • Hankins G.D.
      • Spong C.Y.
      • et al.
      The 2008 National Institute of Child Health and Human Development workshop report on electronic fetal monitoring: update on definitions, interpretation, and research guidelines.
      This cannot remain unquestioned in the face of contradictory evidence. Two recent studies report at least 78 cases of neonatal acidemia despite moderate variability.
      • Cahill A.G.
      • Roehl K.A.
      • Odibo A.O.
      • et al.
      Association and prediction of neonatal academia.
      • Clark S.L.
      • Hamilton E.F.
      • Garite T.H.
      • et al.
      The limits of electronic fetal heart rate monitoring in the prevention of neonatal metabolic acidemia.
      Cahill et al. identified 57 infants with acidemia (defined as pH ≤7.10 on umbilical artery cord gas) out of a series of 5388 consecutive singleton, non-anomalous, cephalic pregnancies who reached the second stage.
      • Cahill A.G.
      • Roehl K.A.
      • Odibo A.O.
      • et al.
      Association and prediction of neonatal academia.
      Of those 57 infants with acidemia, over 90% (52 of the 57 patients) had moderate variability.
      • Cahill A.G.
      • Roehl K.A.
      • Odibo A.O.
      • et al.
      Association and prediction of neonatal academia.
      Clark et al. found that in a series of 120 infants with metabolic acidemia (defined as base deficit >12) at birth, that at least 18% (21 cases) had moderate variability.
      • Clark S.L.
      • Hamilton E.F.
      • Garite T.H.
      • et al.
      The limits of electronic fetal heart rate monitoring in the prevention of neonatal metabolic acidemia.
      Clark et al. write that their findings challenge “decades-old assumptions regarding… the importance of variability in excluding metabolic acidemia.”
      • Clark S.L.
      • Hamilton E.F.
      • Garite T.H.
      • et al.
      The limits of electronic fetal heart rate monitoring in the prevention of neonatal metabolic acidemia.
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      References

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        • Hankins G.D.
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